1. Field of the Invention
This invention relates to the field of door latches, locks and closure apparatus, and in particular to a lever handle lock which becomes temporarily inoperative when exposed to fire.
2. Description of Prior Art
Various designs for doorknobs, handles and such actuators are known in the art. Although globe shaped doorknobs are the most common, various other door latch actuators are known for various purposes. For example, doors which must be opened by persons carrying items are sometimes equipped with lever handles which may be actuated by a person using his or her elbow. Freezer doors and the like are commonly equipped with closures having a mechanism which need only be pushed to open the door from the inside, and include latched levers on the outside.
The present invention concerns door handles of the type which are rotated to open the door, and is particularly adapted for use with lever handles. Horizontally-aligned rotatable lever handles are easily actuated by handicapped persons, by persons carrying various items, and are also convenient for the public at large. Accordingly, horizontally-aligned rotatable lever handles are very useful for hospital doors and the like, and could be advantageously applied to doors in general.
Locks and latches on doors frequently comprise a shaft or spindle member which extends completely through the door near the non-hinged edge of the door, connecting door handles on opposite sides of the door. The spindle is rotated using a knob or lever handle, and a spring-loaded latch bolt is thereby drawn back into the body of the door, or released to mate with a strike mounted in the door jamb. Beyond these simple functions, the closure can be adapted to a number of needs.
The usual external door on a structure (i.e., an "entryway") comprises a lock which can be set to prevent the latch from being actuated by a person outside the structure. The lock permits the closure to be released by a person inside the structure. A person outside the structure can be said to be on the "key side" and a person inside the structure can be said to be on the "non-key side" in the usual situation. Of course, there are also situations where the key side is the interior of the structure, or both sides require keys for one reason or another. For example, where a door comprises a window, easily broken by a burglar, a key may be required on the inside as well, using a "double cylinder" lock. In any event, the closure includes at least a handle and a spindle.
Another possibility concerns the usual door between interior rooms of a structure. There is usually no need to restrict access from either side, and therefore the latch is made operable merely by turning the knob, lever handle or the like on either side of the door. It will be appreciated that the mechanical structure of such a latch mechanism requires substantially fewer parts than that of an external door.
Yet another possibility concerns a door bounding an interior room where an occupant may desire privacy, however, there is little threat of an intruder that might use force or physically damage the latch in an effort to open it. In these situations, a lightweight turnpiece would be employed to controllably prevent the latch from being actuated.
All the foregoing situations may advantageously employ a lever handle actuation system. The present invention applies to each situation and includes a fusible link between the lever handle and spindle which disengages the connection between the handle and spindle in the event of fire. Depending on security requirements, the trim and mounting hardware for the lever handles are preferably made screwless, that is, the screws can be hidden such that the mechanism is free of exposed attachment means on the key side. A novel latch operating mechanism is adapted for use with a lever handle as opposed to a knob, the lever handle being more mechanically demanding than a knob because a lever is inherently non-symmetrically weighted, or "cantilevered".
The general use of fusible links to allow doors to close of their own weight or by the force of springs, to prevent actuation of a latch, and to enable actuation of a latch nonwithstanding a lock, are all known in the art. The particular structures and functions of such fusible link mechanisms vary widely.
U.S. Pat. No. 4,007,954--Erickson discloses a hospital latch employing a fusible link to prevent actuation of a latch in the event of a fire. The device employs a fusible pin for holding a latch bolt stop lever above a position from which it will otherwise drop to foul the latch mechanism. The fusible pin melts in a fire; the latch bolt stop lever falls to foul the latch mechanism; and, theoretically, persons are prevented from blundering into the area of the fire in an effort to escape. Moreover, the now-locked door will not accidentally open due to falling debris and the like.
Inasmuch as Erickson's latch bolt stop lever operates by fouling the latch mechanism when the fusible pin melts, the latch mechanism must be disassembled and the fusible device replaced in order to re-activate the latch mechanism after a fire. It will be appreciated that when such a mechanism is applied to a hospital door, the effect is to lock the door both during and after a fire, until the latch can be disassembled and repaired. Persons who might use the door may become casualties unnecessarily, for example, if a fireman arrives to put out a fire in the hallway. The fireman might have led the occupants to safety had the latch been still operative or easily made operative.
An opposite approach is taken by devices such as that of Horvath, U.S. Pat. No. 4,015,869 (re-issue patent Re. 30,263). Horvath teaches a catch mechanism for a latch (i.e., a strike plate) which is rendered completely inoperative upon melting of a fusible member. The catch opens when the fusible link melts, releasing the door. The interaction of the latch and catch mechanism normally holds the locked door closed. Accordingly, disabling the catch mechanism is equivalent to unlocking the door, and allows occupants an escape path through a door which would otherwise be locked.
The rationale of Horvath and the like, namely unlocking and releasing doors in the event of fire, is sometimes employed to close doors, for example to confine and to starve a fire of oxygen. Many buildings, and in particular public buildings such as schools, have heavy fire doors placed at various positions in the hallways, the fire doors dividing rooms from hallways and the like. Such fire doors may he held open using a fusible member, and when a fire melts the fusible member, the fire door falls shut to confine the fire. Examples of such fusible members are U.S. Pat. Nos. 4,161,804--D'Hooge et al, 3,325,941--Prucha, and others. The same rationale can be employed with windows, such as disclosed in U.S. Pat. No. 2,250,787--Anderson and 4,195,819--Chastanier. Chastanier employs a fusible link in an axial connection between a winched pulley and a brake. Under influence of heat, the axial connection melts, and the pulley is released to allow a window to close.
The present invention employs a fusible link to break an axial connection between a door lever handle and the spindle which actuates the latch. The fusible axial connection is disposed between the lever handle and spindle, rather than centrally in the lock. In this manner, lever handles fusibly connected on both sides of the door can be employed not only for safety, but also to provide an indication of conditions on the opposite side of the door. A fire on a first side of a door will melt the fusible link at a given temperature. Dissipation of heat and losses in conduction from one side of the door to the other will delay melting of the fusible link on the opposite side which occurs after a certain time. Therefore, a fire in a room will eventually cause the lever handle on the opposite side of the door, namely in the hallway, to fall downward, indicating a possible danger to a person opening the door.
Firemen are often injured by explosions when a door enclosing a burning room is suddenly opened. The increase in oxygen available to the fire when a door is opened results in a sudden increase in combustion, and an accompanying blast of heat and flame. Particularly with prior art lever handles, such an explosion can be caused by a jet of water from a fire hose striking the lever handle and actuating the latch. With the present invention, a fireman will be aware of the fact that the fusible link has previously broken, because the lever handle will point downwardly rather than horizontally.
Should a jet of water be briefly directed against a lever handle while the fusible link is melted, the lever handle will rotate without actuating the latch mechanism. A substantial application of water will cool and re-harden the fusible member and re-attach the lever handle to the door. Therefore, should the fireman so desire, the door can be opened, even though the fusible link was melted. Additionally, a fire present on the hallway side of the door will create the same effect on a lever handle. However, a person inside the room will have an opportunity of attempting an escape by actuating the level handle inside before its fusible link melts.
Lever handles are desirable over doorknobs because they are more easily actuated, for example by handicapped persons and persons carrying items of various descriptions. Lever handles place an unusual strain on a latch or lock mechanism, however, because they are cantilevered and their weight and "moment arm" must be opposed by the latch mechanism. The longer the handle, the greater the moment arm and the greater the strain on the latch mechanism. In the prior art, no specific provisions were made to accommodate lever handles on latches or locks. Rather, the same latches and locks which were used with doorknobs were merely equipped with lever handles. The strain of the lever handles required that a heavy duty latch/lock mechanism be employed, or that the lever handles be relatively light or counterweighted. Spring mechanisms were employed to hold a lever handle in a desired position. Reference may be made to U.S. Pat. No. 1,769,314--Rymer, disclosing a spring member adapted to resist rotation of a lever handle from a fixed "home" position. In order to ensure that Rymer's lever handle remains attractively horizontal as it is initially mounted, a heavy duty spring and latch mechanism are required, or the lever handle must be made light in weight. Even if these precautions are taken, with use and wear, the weight of the lever handle will operate against the spring to cause the "home" position of the lever handle to droop lower and lower. Maintaining an exact horizontal handle is difficult because the handle is generally attached to the squared spindle shaft via a set screw, whereby the handle will be mountable only at one of four angles unless special provision is made for a continuously variable, lockable position, for example, a set screw and cylindrical shaft arrangement.
The prior art teaches initially setting lever handles at a home position somewhat above the home position which would be maintained by the spring without the weight of the lever handle. When the lever handle is installed, the weight theoretically offsets the placement of the "home" position above horizontal, and as a result the lever handle rests at exactly horizontal. An offset of seven degrees is typical. Unfortunately, this practice does not account for wear and fatigue in the spring. Of course, a latch having a very strong and heavy duty spring can be designed such that the effects of wear and metal fatigue on the spring will be unnoticed. Such a latch would be unacceptably difficult to operate especially for handicapped persons or persons with their hands full.
The present invention provides a positive stop for one or both lever handles. A hub member mounted to the spindle has a fixed rigid extension which is forced against a pin, rigidly mounted to the casing, by means of a spring. The alignment of the lever handle is therefore exactly set to a home position which does not change with wear and age. The alignment of the spindle being set, the lever handle need not be adjustable or continuously positionable.
The prior art has conceived of dead bolt locks having both the latch mechanism and the dead bolt mechanism as part of the same unit. In many such devices, it is necessary to unlock the lock mechanism in order to operate the latch mechanism even from the non-key side. In order to avoid such a requirement, lock manufacturers have on occasion designed locks which are operable from the non-key side, without regard to the fact that the key side is locked. Often a push button selection on the face of the lock is provided in order to select between operating modes for the latch and/or lock. The present invention employs inside and outside lever handles mounted on co-axial spindles which are threadably rather than rigidly connected, enabling relative independent rotational movement. Operating the lever handle on the non-key side retracts the deadbolt and latchbolt mechanisms simultaneously.
The present invention employs positively positioned, fusibly attached lever handles on a novel lock/latch mechanism which further comprises a screwless mounting, for the ultimate in security and convenience without loss of attractiveness and safety.